Generally, a conventional automatic transmission for a vehicle includes a torque converter, a multi-stage gear shift mechanism connected to the torque converter, and a plurality of friction elements actuated by hydraulic pressure for selecting a gear stage of the gear shift mechanism.
In such hydraulic control systems, hydraulic pressure generated by a hydraulic pump is selectively supplied to each friction element by a plurality of control valves such that automatic shifting is realized in accordance with a driving state of the vehicle and engine throttle opening.
The above hydraulic control system generally comprises a pressure regulating controller for controlling hydraulic pressure generated by the hydraulic pump, manual and automatic shift controllers for selecting a shift mode, a hydraulic pressure controller for controlling shift response and shift quality, a damper clutch controller for actuating a damper clutch of the torque converter, and a hydraulic pressure distributor for supplying an appropriate amount of hydraulic pressure to each of the friction elements.
The hydraulic pressure distributor distributes a variable amount of pressure in accordance with an ON/OFF or duty operation of solenoid valves by a transmission control unit such that shift control is realized.
In such a hydraulic control system, because at least one input element is being operated in a first speed of a drive D range, a shifting operation is performed in a powertrain and torque is transmitted to wheels of the vehicle.
As a result of this transmission of torque, a creep state results in which the vehicle moves even when an accelerator pedal is not depressed by the driver. Therefore, a brake pedal must be kept depressed in order to maintain the vehicle in a standstill state. This can be very inconvenient when needing to stop for long periods while keeping the engine running up as when stopped at a red light or stuck in traffic.